Question about using epoxy primers
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 8,246
Likes: 114
From: Watkins Glen NY
Question about using epoxy primers
Please don't flame me guys, because I "think" I know the answer to this, but the more I think about it the more doubt I have.
I'm not a painter; the extent of my paint is one corvette with acrylic enamel, and one with 2K primer and single stage urethane. Both were stripped clean and came out fine, but no doubt I am a noob in the paint world.
When using epoxy primer over bare fiberglass,, do you wet sand it before applying a 2K primer? Or leave it alone and wet sand it all after both primers are applied?
I say that the epoxy gets sanded before the next step, and a friend of says "no", leave it alone and apply the 2K primer directly over the unsanded epoxy. Then wet sand before the color. Which is correct?
Thanks, Joe
I'm not a painter; the extent of my paint is one corvette with acrylic enamel, and one with 2K primer and single stage urethane. Both were stripped clean and came out fine, but no doubt I am a noob in the paint world.When using epoxy primer over bare fiberglass,, do you wet sand it before applying a 2K primer? Or leave it alone and wet sand it all after both primers are applied?
I say that the epoxy gets sanded before the next step, and a friend of says "no", leave it alone and apply the 2K primer directly over the unsanded epoxy. Then wet sand before the color. Which is correct?
Thanks, Joe
Pro
Joined: Jan 2010
Posts: 533
Likes: 18
From: Boca Raton Florida
Fellow noob. I understand the epoxy doesn't need to be sanded if you spray the primer within 7 days. Epoxy that has cured longer than that needs to be sanded. May not be true for all brands so I'd check the tech sheet for the one you are using. Flame-free?
Melting Slicks
Joined: Feb 2007
Posts: 2,136
Likes: 62
From: West Kingston RI
Also a fellow noob here but this is my understanding as well.
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 8,246
Likes: 114
From: Watkins Glen NY
The product sheet reads that it must be scuffed and reapplied if allowed to sit more than three days....
I guess what my question is, "should" it be wet sanded before applying a 2K primer, even within the three day window?
It would seem to me that it would not be smooth enough after it dries (haze) to just shoot more paint over it without sanding it smooth.
Melting Slicks
Joined: Jun 2009
Posts: 2,709
Likes: 3
From: Savannah GA
I try and let all primer coats dry completely before the next coat goes on... therefore I scuff sand or wet sand each coat before going to the next....I worked in body repair when lacquer based primers were the norm; they shrink terribly as they age causing a range of problems from sand scratch telegraphy to actual delamination of the primer from the substrate if film thickness exceeded flash time. My understanding of many of the "new tech" substrates leads me to believe that some shrinkage and "settling" may occur in some instances... just seems prudent not to "push the envelope" by rushing; especially since the car you're working on is your own, and there is really no time pressure to complete the repair. So slow down, let things dry well, sand between applications and end up with an error free finish that will last for years issue free.
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
Epoxy primers will accept urethane primer directly over an un-sanded finish unless the curing window is reached. Actually, I don't wait very long because I don't want to chance having any place crevasse etc. that even remotely approaches that window. So, I apply urethane primer directly over the epoxy as soon as it flashes, just like any other coat, or early the next day.
Pro
Joined: Jan 2010
Posts: 533
Likes: 18
From: Boca Raton Florida
Flame free
The product sheet reads that it must be scuffed and reapplied if allowed to sit more than three days....
I guess what my question is, "should" it be wet sanded before applying a 2K primer, even within the three day window?
It would seem to me that it would not be smooth enough after it dries (haze) to just shoot more paint over it without sanding it smooth.
The product sheet reads that it must be scuffed and reapplied if allowed to sit more than three days....
I guess what my question is, "should" it be wet sanded before applying a 2K primer, even within the three day window?
It would seem to me that it would not be smooth enough after it dries (haze) to just shoot more paint over it without sanding it smooth.
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 8,246
Likes: 114
From: Watkins Glen NY
After stumbling around some threads using a few searches that actually returned pertinent threads, I think the general belief is to not sand it, and apply the 2K right over it, then sand to smooth.
I think a couple of words used here made my search reading more clear: "accepts" and " bonds" when referring to paint applied over the top of epoxy.
So, I think I will leave the epoxy be, and do all of my wet sanding on the primer coats that follow. Thanks for the replies!
Joe
I think a couple of words used here made my search reading more clear: "accepts" and " bonds" when referring to paint applied over the top of epoxy.
So, I think I will leave the epoxy be, and do all of my wet sanding on the primer coats that follow. Thanks for the replies!
Joe
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